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Forum Replies

  1. Very clear and easy to understand. Great job :slight_smile:

  2. Hi Rene,
    What happens when Portfast is enabled on a port but BPDU filter is not globally enabled and the port receives a BPDU.


  3. Chandru,
    The port will lose its portfast status, and will continue to function like a normal port (without Portfast). It will not be disabled unless BPDU Guard was also enabled.

    FYI: Rene has a Lesson related to this topic here

  4. Hi Rene,

    It means Portfast enabled interface still sends and recevies BPDU.
    what happens when We configure BPDU filter ?

  5. andrew says:

    There are actually two modes of BPDU Filter: Per port (dangerous) and globally.

    In the port mode, the switch will not send or receive BPDUs (which essentially disables the STP process) on the port in question. Configuring BPDU Filtering in port mode would prevent the switch from detecting a loop involving the port where it is enabled. This is why this option is considered dangerous and is generally avoided.

    In global mode, this command is paired with portfast as follows:

    switch(config)#spanning-tree portfast bpdufilter default
    switch(config)#spanning-tree portfast default

    This prevents interfaces in portfast mode from sending BPDUs. However, if a BPDU is received on such an interface, the interface will lose its PortFast state, and outgoing BPDU filtering is disabled.

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